1. Field of the Invention
This invention relates to laminated packaging and more particularly to continuously moving rolls of printed material and pre-formed packing material, the relative movement of which must be tightly controlled so as to be in registration with one another in the finished package.
2. Description of the Prior Art
Packaging of the type known as "bubble" or "blister" often comprises a foil or paper printed portion which must be held in registry with a pre-formed transparent plastic portion. This is particularly important in those packages where the bubble portion in the pre-formed transparent plastic which contains the product must line up with the decorative material printed on the foil or paper, such as packaging for pharmaceutical samples.
In laminating such a product, registration is a problem because the materials cannot normally be accurately controlled in terms of their stretching during processing. Various attempts at doing this have been tried including the following. A machine produced by Bosch which is used on "soft" foil without paper backing, relies on a cam type ram to create intermittant stretching. In accordance with this machine as shown schematically in prior art FIG. 1, the material being processed passes between the jaws 100,102 of the ram 104. The ram has two cylindrical bars 106,108 spaced apart on one head with the axis of the cylinders being transverse to the direction of travel of the material 110. On the other head there is a single cylindrical bar 112 with its axis transverse to the direction of movement of the material. They are positioned as shown so that the two bars bracket the single bar. When the ram travels toward the material in the direction of the arrow shown in the figure, it can cause the material to be stretched by adjusting the amount of force against the faces of the material as it passes between the three rollers in contact with it. If the ram hits with great force, it may penetrate further into the material against the clamp resistance of the pads which grip the material intermittently, thereby stretching it even more, such a device would normally tear paper.
In another machine produced by an Italian company, the continuously moving material has a drag placed upon it by a moveable vacuum roller; as shown schematically in prior art FIG. 2. In this device material 200 proceeds from a main feed roll 202 around several vacuum rolls 204,206 to a seal roll 208. Between the main feed roll and the first vacuum roll there is an eye 210 which may sense a printed dot on the material. All of these rolls normally run at the same speed. If the eye senses a change is necessary, then the first vacuum roll 204 is slowed by one percent by a change of gears activated by the eye. Thus this design, with fixed gear ratios, limits control within fixed parameters.
Other prior art machines do not run continuously, but rather must stop and adjust the length and position of the materials with respect to one another. In such machines, known as "flat seal" machines, the material is grabbed and pinched. If the electric eye sensors indicate that the foil and plastic are too far out of alignment, then the machine adjusts with a fixed stop adjustment (like a vernier) which adjusts the length by not allowing as much movement. However, to my knowledge this was never done on a rotary machine for continuously moving materials.
Other problems in the prior art relate to the conditions under which these machines operate, such as the heat and vibration, which tend to throw off the printing alignment and interfere with normal printing operations.